The Universal Mobile Telecommunications System (UMTS) is a mainstream 3G wireless communications standard formulated by the Third Generation Partnership Project (3GPP). In order to meet an ever-increasing rate requirement of users, a High Speed Packet Access (HSPA) technology, including High Speed Downlink Packet Access (HSDPA) introduced in Release 5 and High Speed Uplink Packet Access (HSUPA) introduced in Release 6, is introduced to the UMTS to improve spectral efficiency, and mainly provides a higher data rate, a lower delay, and a higher system capacity.
In 3GPP Release 7, a Continuous Packet Connectivity (CPC) feature supporting discontinuous transmission/discontinuous reception is introduced. This feature allows discontinuous reception and transmission for a UE (user equipment). When there is no data being transmitted, an uplink discontinuous transmission function allows termination of DPCCH (dedicated physical control channel) transmission in the uplink, so as to reduce uplink interference. In order to maintain power control and link synchronization, the UE periodically sends DPCCH control information within a discontinuous transmission period. With further in-depth study on the 3GPP standards, a Further Enhanced Uplink Enhancement (Further EUL Enhancement) feature is being studied in 3GPP Release 12, where there is a technology called a lean carrier and is also called a dedicated secondary carrier; and the core idea of this technology lies in that, when a UE does not send data, a DPCCH is no longer periodically sent either.
Through repeated research and practice, it is discovers that, in the dedicated secondary carrier scheme, a UE sends a DPCCH only when transmitting data in the uplink; therefore, when the UE initiates uplink transmission, a base station cannot control uplink transmission power because there is no data scheduling for the UE for a relatively long time before.